Nikos Alexandris wrote: > > > I don't get the desired results... The output is too bright from what one > > > would expect it to be. > > > > > > Any recommendations? Hamish: > > I've never used it for MODIS, but you could try i.landsat.rgb to see if > > that helps. (it wants three 0-255 bands, it doesn't care about it being > > LANDSAT or not) Nikos: > Will this approach enable a correction for terrain as well? I don't see > how I can incorporate elevation data or anything relevant. > > I used the cosine correction approach which is described in GRASS-GIS in > order to correct a MODIS image. But the result is over-corrected (!) as > mentioned also in the book.
No, i.landsat.rgb does not touch the data, it only normalizes the color tables while preserving the relative hues (-p). If your image is simply over-bright it can lower the visual brightness*, but not fix the contrast. [*] actually it is (mostly) designed for brightening dark images, so you would need to edit the script and swap the hard-coded MIN=`r.univar percentile=2` to $((100-BRIGHTNESS)) and MAX=`r.univar percentile=$BRIGHTNESS` to "2" to make it dimmer. Or get rid of the "2" and cut from both ends with $BRIGHTNESS. I guess we could add a new flag to the module to do that if there was demand. The result is dependent on the image, so not much use for quantitatively comparing a time series of images with different reflectance angles. Hamish ____________________________________________________________________________________ Be a better sports nut! Let your teams follow you with Yahoo Mobile. Try it now. http://mobile.yahoo.com/sports;_ylt=At9_qDKvtAbMuh1G1SQtBI7ntAcJ _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user